This application is based on and claims priority to Japanese Patent Application No. 2001-200430, filed Jul. 2, 2001, the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
The present invention is directed to a valve timing control for an engine, and more particularly to an improved valve timing control for an engine that includes a variable valve timing mechanism.
2. Description of Related Art
Recently, four-cycle engines with variable valve timing have become more widely used. Typically, a four-cycle engine includes one or more intake valves and exhaust valves moving between an opening position and a closing position of intake ports and exhaust ports, respectively. One or more camshafts can be provided to actuate the valves in a timed manner. With the intake valves opened, air is introduced into combustion chambers of the engine through the intake ports. With the exhaust valves opened, exhaust gases are discharged from the combustion chambers through the exhaust ports.
The engine can include a hydraulically operated variable valve timing (VVT) mechanism that can change the opening and closing timing of respective valves by changing an angular position of the camshaft relative to the crankshaft. A control module such as, for example, an electronic control unit (ECU) is used to control the VVT mechanism under various control strategies. For example, the ECU can control the VVT mechanism adjust the valve timing between a fully advanced position and a fully retarded position. The fully advanced position is used for relatively high engine speeds to ensure high charging efficiency and high performance of the engine. The fully retarded position is used for relatively low engine speeds to ensure high combustion efficiency, fuel economy and good emission control. Otherwise, the ECU controls the VVT mechanism to set the valve timing at a position between the fully advanced position and the fully retarded position in response to a running condition of the engine.
The control strategy can be stored in the ECU as a control routine, or the ECU can be hard-wired to perform the desired control. With the output of appropriate sensors, the ECU can thus perform feedback control to adjust the VVT mechanism in accordance with a desired control characteristic.
The VVT mechanism can comprise an electrically operable unit such as, for example, a solenoid actuator that varies a hydraulic flow in the VVT mechanism. Typically, the solenoid actuator is connected to a battery which supplies electric power not only to the solenoid actuator, but also to a number of other electrical components.
One aspect of the present invention is the realization that in applications where another electrical accessory is used intermittently during operation of the engine, the accessory can cause the voltage in the corresponding electrical system to drop and thereby cause interference with accurate VVT control.
For example, marine drives such as outboard motors and stern drives, are relatively more vulnerable to a voltage drop. Typically, a marine drive must fit into a relatively narrow space and thus can only include a small size alternator. Such an alternator cannot supply large power to the battery. Accordingly, sufficient current cannot be supplied to electrical components of the marine drive if, for example, multiple electrical components are operated simultaneously. Occasionally, operation of the electrical components connected to the battery of the marine drive can consume so much power that some of the energy stored in the battery is drained while the engine is operating. Such electrical accessories can include, for example but without limitation, lighting implements and a net winch can be used when the engine operates.
Outboard motors typically include a hydraulic tilt and trim adjustment system which can tilt (raise or lower) a housing unit thereof. The tilt system can be frequently and intermittently activated during operation of the engine. Such a tilt system typically comprises an electric motor that drives a hydraulic pump. Such an electric motor can draw a relatively large current.
When such an electric accessory is activated, the resulting voltage drop in the electrical system can cause a significant problem with the VVT mechanism operation. For example, as noted above, the solenoid of the VVT mechanism draws power from the battery. Thus, when there is a voltage drop in the electrical system, the performance of the solenoid is affected. In particular, the solenoid can react more slowly than expected, and thus fail to provide the actuation needed to achieve the desired VVT adjustment.
A need therefore exists for an improved valve timing control for an engine that can control a VVT mechanism accurately even if a voltage drop occurs at the power source of the VVT mechanism.
In accordance with another aspect of the present invention, an internal combustion engine comprises an engine body. A movable member is movable relative to the engine body, the engine body and the movable member together defining a combustion chamber. The engine body defines intake and exhaust ports communicating with the combustion chamber. An air induction system communicates with the combustion chamber through the intake port. An exhaust system communicates with the combustion chamber through the exhaust port. An intake valve is arranged to move between an open position and a closed position of the intake port. An exhaust valve is arranged to move between an open position and a closed position of the exhaust port. A valve actuator is arranged to actuate one of the intake valve and the exhaust valve. A valve actuator adjustment mechanism includes an electric actuator configured to adjust an actuating timing of the valve actuator at which the valve actuator actuates the intake valve or the exhaust valve. A control module is configured to control the electric actuator based upon a control characteristic. At least one sensor is configured to detect when a second electrical component is operated. The control module is configured to adjust the control characteristic when the second electrical component is operated.
In accordance with another aspect of the present invention, an outboard motor comprises a housing unit, and an internal combustion engine supported by the housing unit. A bracket assembly is adapted to mount the housing unit on an associated watercraft for a tilt movement about a generally horizontally extending tilt axis. A tilt mechanism is configured to tilt the housing unit about the tilt axis. The tilt mechanism includes an electrical component. The engine comprises an engine body, and a movable member movable relative to the engine body. The engine body and the movable member together defining a combustion chamber. The engine body also defines intake and exhaust ports communicating with the combustion chamber. An air induction system communicates with the combustion chamber through the intake port. An exhaust system communicates with the combustion chamber through the exhaust port. An intake valve is arranged to move between an open position and a closed position of the intake port. An exhaust valve is arranged to move between an open position and a closed position of the exhaust port. A valve actuator is configured to actuate either the intake valve or the exhaust valve. A hydraulic change mechanism is configured to change an actuating timing of the valve actuator at which the valve actuator actuates the intake valve or the exhaust valve. The change mechanism includes an electrically operable member varying a hydraulic flow in the change mechanism to change the actuating timing of the valve actuator. The electrically operable unit being adapted to be supplied with electric power from a power source. A control module is configured to control the electrically operable member based upon a control characteristic. The electrical component is adapted to be supplied with electric power from the power source. A tilt sensor is configured to sense when the electrical component is operated and to send a signal indicative that the electrical component is operating to the control module, the control module adjusting the control characteristic in accordance with the signal from the sensor.
A further aspect of the present invention is directed to a method for controlling an internal combustion engine. The engine includes intake and exhaust valves, a valve actuator arranged to actuate the intake and exhaust valves, and a hydraulic change mechanism configured to change an actuating timing of the valve actuator at which the valve actuator actuates at least one of the intake valve and the exhaust valve. The method includes changing the actuating timing based upon a control characteristic, supplying electric power to an electrically operable member of the change mechanism from a power source, and sensing when an electrical component connected to the power source is operated to receive the electric power from the power source. Additionally, the method includes adjusting the control characteristic when the electrical component is operated.
Another aspect of the present invention is directed to a method for controlling an outboard motor. The outboard motor includes a tilt mechanism and an internal combustion engine. The engine includes intake and exhaust valves, a valve actuator arranged to actuate the intake and exhaust valves, and a hydraulic change mechanism arranged to change an actuating timing of the valve actuator at which the valve actuator actuates at least one of the intake valve and the exhaust valve. The method includes changing the actuating timing based upon a control characteristic, supplying electric power to an electrically operable member of the change mechanism from a power source, supplying electric power to an electrical component of the tilt mechanism from the power source, and sensing the electrical component is operated to receive the electric power from the power source. The method also includes adjusting the control characteristic when the electrical component is operated.
In accordance with a further aspect of the present invention, an engine includes an engine body, a shaft rotatably journalled for rotation at least partially within the engine body, and at least one valve seat. At least one valve is configured to move between an open position relative to the valve seat and a closed position relative to the valve seat. A valve actuator is configured to move the valve between the open and closed positions in accordance with a timing relative to rotation of the shaft. A timing adjustment device is powered by an electrical system and is configured to adjust the timing. A control module is configured to determine a target timing and to send an output signal to the timing adjustment device to adjust the timing towards the target timing. At least a first electrical component is powered by the electrical system. The first electrical component is selectively operable by a user and causes a significant voltage drop in the electrical system when activated. Additionally, the engine includes means for adjusting a magnitude of the output signal when the first electrical component is activated